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How the power of pairing can tackle cancer

A new theranostic imaging technique, offering unprecedented levels of accuracy in diagnosing advanced prostate cancer, will soon be available for treating it.

Dr Yong Du

Consultant in Nuclear Medicine and PET/CT MBBS MSc PhD

Dr Philip Camilleri

Consultant Clinical Oncologist MRCP M.D. FRCR

Mr Alan Doherty

Consultant Urologist MD BS, Bsc, MD, FRCS(Urol), FEBU

The theranostic tool is being hailed as a major step forward in diagnosis and treatment of metastatic castration resistant prostate cancer (mCRPC), which has returned and spread after standard androgen-deprivation treatment has become ineffective.

Prostate cancer is the most commonly
diagnosed cancer in males and the second leading cause of cancer mortality
among men. While many
patients are cured of prostate cancer, a significant proportion progress
towards CRPC.

How does this pairing
technique work?

The technique involves ‘pairing’ a
radio-isotope with prostate
specific membrane antigen (PSMA), a protein expressed by prostate tissue,
including cancerous tissue, to create a radiotracer for injection into a PET/CT
scanning patient.

Pairing PSMA with gallium, as Ga-68 PSMA,
gives a highly sensitive tracer that seeks out cancerous tissue, delivering a more
accurate picture of the size and location of areas of prostate cancer than
previously possible.

Pairing PSMA with lutetium creates Lu-177 PSMA, a tracer which can seek out prostate cancer and then destroy the cancer cells – a demonstration of theranostics and a highly personalised treatment.

Earlier, more accurate prostate cancer diagnoses

Gallium-PSMA PET/CT scans are already used routinely
for diagnosing, staging and decision-making (along with Lu-177 PSMA therapy) in
CRPC by GenesisCare Australia, and for diagnosis in London, and
GenesisCare Windsor, although it is not funded
on the NHS.

The
technique can detect otherwise-invisible cancers. Mr Alan Doherty, Consultant
Urologist and Surgeon, says: “Sometimes a raised level of prostate
specific antigen indicates that prostate cancer has returned, even after
prostate removal, or the cancer is invisible with
most imaging methods. Gallium-PSMA
PET/CT scans can detect these cancers.”

He
adds: “I would like to recommend the gallium-PSMA PET scan to all my
patients with suspected prostate cancer.”

Dr Camilleri says: “Traditional scans are less
sensitive – choline PET scans require a much larger mass of cancer before they
detect it.”

The new technique also shows advantages over bone
scanning. “Ga-68 PSMA scans can detect cancer in the bones – common in
prostate cancer – but elsewhere too,” says Dr Camilleri. “It also
differentiates between bone damage caused by cancer and that caused by other
more common conditions, which bone scanning cannot.”

Faster cancer
treatment, fewer side effects

Dr Yong Du
is a consultant in nuclear medicine who has used radiopharmaceuticals to treat
around 250 patients with mCRPC – more than anyone else in the UK. “This
new theranostic tool delivers more accurate assessment and treatment for mCRPC”,
he says.

“It
enables accurate targeting, reducing delivery of radiation to healthy tissue.
It is more effective and less toxic than conventional treatments, although a
small percentage of patients might develop treatment-induced xerostomia (dry mouth).”

“Outpatient assessment, plus treatment,
can be achieved within two working days. People can be discharged to their home sooner – particularly
valuable for patients travelling from other parts of the UK and abroad.”

Access to the therapy in the UK

At
present, PSMA-lutetium treatment is being trialled on patients with mPCRC but
GenesisCare will introduce it more widely in
the UK soon.

“Currently
PSMA-lutetium treatment is only licenced for use in end-stage prostate cancer.
Its effectiveness is yet to be fully proven, but it is already showing good
results,” says Mr Doherty.

As
Dr Camilleri says: “Lutetium
kills cancer cells. It is not a complete cure, but it looks like it can keep
patients alive, with a better quality of life, for longer.”